Supported nanoparticles and nanosheets of MgAl LDH as co-catalyst in the dry reforming of methane

Oz M. Gazit, Chemical Engineering, Technion, Haifa, Israel
Anup Tathod, Chemical Engineering, Technion, Haifa, Israel

Layered double hydroxides (LDH) are widely used as catalysts in various base catalyzed reactions, anion exchangers, catalyst supports, adsorbents and as fillers for polymeric materials. For the dry reforming of methane (DRM), the positive surface charge of LDH materials gives it the capacity to better resist carbon formation, which is one of the main limiting factors of DRM. Moreover, the flexible composition of LDH materials provides means to tune their catalytic performance by incorporation co-catalysts. The limiting factor of LDH materials is their relatively low thermal stability, which is an important factor in DRM and in many other high temperature reactions. To overcome this limitation and provide enhanced catalytic performance we synthesize LDH nanosheets (NSs) and nanoparticles (NPs) and support them on the surface area of negatively charged metal oxide supports. The use of nanoscale LDH exposes more low coordination sites, which are beneficial for DRM catalysis and allows us to control the growth and stability of the catalytic Ni nanoclusters. The ability to control the number of LDH layers enables us to tune metal support interactions.
Herein we present an efficient and highly reproducible method for the synthesis of LDH NSs and NPs, while avoiding the use of organic structure directing agents. By varying the nucleation temperature between 60 and -55°C in conjunction with a fast addition we can obtain narrowly distributed isolated nano-LDH crystallites in the range of 20-200nm. The results are correlated with classical nucleation and growth theory. Nickel NPs are synthesized on the supported LDH NPs/NSs and employed as catalysts for DRM. Finally we use the tunable nature of the LDH materials to control the catalyst structure and in turn manipulate catalytic performance. Materials are tested by DLS, XRD, HR-TEM, TPR, physisorption and DRM catalysis.